1. Field of the Invention
The invention relates generally to an unweighting assembly for providing support to a patient during rehabilitative exercises. More specifically, the invention relates to a support harness and a harness assembly for partially or completely unweighting a patient during various stages of rehabilitation.
2. Related Technology
Rehabilitation generally includes two main stages of progression, crawling and walking. During crawling, the patient is obviously in a low position where his/her trunk (defined as the area between the shoulders and the waist) is generally horizontal. During walking, the patient is obviously more upright, with his/her trunk in a generally vertical position.
Currently-known unweighting systems generally include two designs. The first design is a pelvic support system that includes support shorts that encircle the user's pelvis in a manner not unlike a diaper or a pair of shorts and a pair of support straps connected to the support shorts. Each of the support straps is connected to the support shorts at a connection point near the patient's hips, respectively. More specifically, typically the connection points are each located at or near the rear side of one of the patient's hips, between the lower back and the buttocks.
While crawling with a pelvic support system, the forces acting on the patient are primarily or completely concentrated on the patient's pelvis, thereby potentially leading to undesirably stress points that may cause injury or discomfort. Additionally, because the harness only includes two connection points and two support straps, the patient is only supported along a single axis. Therefore, the patient is free to pivot about the axis and may experience difficulty maintaining his/her body in a desired configuration.
For example, while crawling, the patient may have difficulty maintaining his/her torso in a generally horizontal configuration because it is difficult or impossible for the patient to maintain his or her balance. More specifically, if the pelvic support connection points are not positioned such that upper portion of the patient's body, which is positioned in front of the connection points, does not have the same weight as the lower portion of the patient's body, which is positioned behind the connection points, then the patient will tip forwards or backwards. Because different patients have different body sizes and proportions, it may be difficult to position the pelvic support such that the patient is in equilibrium. Additionally, even if the patient is in equilibrium while stationary, it will be nearly impossible for the patient to maintain the equilibrium while crawling. Therefore, the patient will be forced to exert energy supporting him/herself in a generally horizontal position while crawling, thereby reducing the amount of energy that may be used for productive, rehabilitative purposes.
The patient may also experience difficulty maintaining a desired body position while walking in an upright position. For example, because the pelvic support connection points are relatively low along the vertical axis, namely near the patient's hips, the patient will be required to hold his/her upper body in a generally vertical position to avoid flipping forwards or backwards due to moment of inertia forces acting on the patient's upper body about the horizontal axis. In other words, the moment arm between the hips and the patient's upper body is relatively large and causes generally high torque forces if the patient leans slightly forward or backward. As another example, because pelvic support connection points are on the patient's back, they are slightly behind the patient's center of gravity and the patient may be biased forward even if he/she maintains his/her upper body in a generally vertical alignment. Therefore, as with the crawling position, the patient is required to expend energy maintaining a desired body position and is potentially susceptible to falling.
The second design is an over-the-shoulder strap harness that includes two relatively narrow shoulder straps, two relatively narrow crotch straps, and a connector strap portion connecting the respective straps. The harness includes a pair of connection points, one on each shoulder, so that the patient is supported while in an upright position. However, the strap harness design does not include any connection points on the patient's back side and therefore cannot be used to effectively support the patient while he/she is in a crawling position. Furthermore, the crotch straps in this design are relatively thin straps that may cause high stress concentrations on the patient's thighs and/or groin area. The stress concentrations may be especially undesirable in patients having partial or complete paralysis in portions of their body because these patients may be unable to tighten their muscles in the areas of the straps, thereby making their bodies more susceptible to the effects of high stress concentrations.
It is therefore desirable to provide an improved support harness that is able to effectively support a patient while he/she is in a crawling position and in an upright position. Additionally, it is desirable to provide an improved support harness that creates generally even force distribution and avoids relatively high stress concentrations acting on the patient's body.